In late years, a transparent organic polymer material has been used as a transparent material in place of an inorganic glass. When such a material is used, for example, fora resin for optical, there has been demanded the resin having required general properties such as transparency, thermal properties, mechanical properties and the like, while attaining a high refractive index.
A technique concerning such a resin has been disclosed in Patent Document 1. In the Document, a metal-containing thietane compound has been disclosed. Furthermore, a resin for optical having a high refractive index exceeding a refractive index (nd) of 1.7 has been disclosed.
Patent Document 1: International Publication Pamphlet No. 2005/095490
Patent Document 2: Japanese Patent Laid-open No. 2003-327583